1. Field of the Invention
The present invention relates to telemetry systems for use in wellbore operations. More particularly, the present invention relates to telemetry systems for providing power to downhole operations and/or for passing signals between a surface control unit and a downhole tool positionable in a wellbore penetrating a subterranean formation.
2. Background Art
The harvesting of hydrocarbons from a subterranean formation involves the deployment of a drilling tool into the earth. The drilling tool is driven into the earth from a drilling rig to create a wellbore through which hydrocarbons are passed. During the drilling process, it is desirable to collect information about the drilling operation and the underground formations. Sensors are provided in various portions of the surface and/or downhole systems to generate data about the wellbore, the earth formations, and the operating conditions, among others. The data is collected and analyzed so that decisions may be made concerning the drilling operation and the earth formations.
Telemetry systems are utilized in the analysis and control of wellbore operations and allow for analysis and control from a surface control station that may be located on site, or may be remote. The information gathered allows for more effective control of the drilling system and further provides useful information for analysis of formation properties and other factors affecting drilling. Additionally, the information may be used to determine a desired drilling path, optimum conditions or otherwise benefit the drilling process.
Various telemetry tools allow for the measuring and logging of various data and transmission of such data to a surface control system. Measurement while drilling (MWD) and logging while drilling (LWD) components may be disposed in a drill string to collect desired information. Various approaches have been utilized to pass data and/or power signals from the surface to the measurement and logging components disposed in the drillstring. These may include, for example, mud-pulse telemetry as described in U.S. Pat. No. 5,517,464, wired drill pipe as described in U.S. Pat. No. 6,641,434, and others.
Despite the development and advancement of telemetry devices in wellbore operations, there remains a need to provide additional reliability and telemetry capabilities. Like any other wellbore device, telemetry devices sometimes fail. Additionally, the power provided by telemetry devices may be insufficient to power desired wellbore operations. Moreover, it is often difficult to extend communication links through certain downhole tools, such as drilling jars. Furthermore, the couplings used in power and/or data transmission lines in a drillstring are often exposed to a harsh environment, such as variations and extremes of pressure and temperature, contributing to the failure rate of such transmission systems.
Accordingly, there remains a need to provide telemetry systems capable of extending across portions of the drill string and/or downhole tool. In some cases, it is desirable to provide redundancy to the existing telemetry system and/or to bypass portions of existing systems. It is further desirable that such a system provide simple and reliable operation and be compatible with a variety of tools and bottom hole assemblies (BHAs). Such techniques preferably provide one or more of the following, among others: increased speed, improved signal, reduced attenuation, increased reliability, increased data rate, protection for components of the downhole tool, reduced lost in hole time, easy access to telemetry components, synchronization between shallow and deep components, versatility, higher frequency content, reduced delay and distance to telemetry components, increased power capabilities and/or diagnostic capabilities.